Re: [Intel-gfx] [PATCH 3/5] drm/i915/icl: Cross check the combo PLL WRPLL parameters wrt. hard-coded PLL freqs

Ville Syrjälä
2020-10-01T17:01:08Z

On Thu, Oct 01, 2020 at 07:44:29PM +0300, Ville Syrjälä wrote:
> On Tue, Sep 29, 2020 at 03:29:27AM +0300, Imre Deak wrote:
> > When selecting the WRPLL dividers for a given port clock/PLL freq, the
> > hard-coded PLL freq in a table entry can be calculated using the rest of
> > parameters in the same entry. Cross-check if the hard coded values match
> > what we calculate with the formula.
>
> We've never done this on any other plaform I think. Why is this special?

I think if we do this we should do at init time for all such tables.
Ideally we'd do it at compile time but no constexpr in C :(

> Also, shouldn't the state checker catch this anyway?
>
> >
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> > drivers/gpu/drm/i915/display/intel_dpll_mgr.c | 26 ++++++++++++++++++-
> > 1 file changed, 25 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > index e3370c8dccc8..ded2b2dfe319 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
> > @@ -3002,6 +3002,30 @@ static const struct skl_wrpll_params tgl_tbt_pll_38_4MHz_values = {
> > .pdiv = 0, .kdiv = 0, .qdiv_mode = 0, .qdiv_ratio = 0,
> > };
> >
> > +static int icl_wrpll_ref_clock(struct drm_i915_private *i915);
> > +
> > +static bool icl_dp_combo_pll_clock_match(struct drm_i915_private *i915, int clock,
> > + const struct icl_combo_pll_params *p)
> > +{
> > + int ref_clock = icl_wrpll_ref_clock(i915);
> > + int pll_freq;
> > + u32 pdiv;
> > + u32 qdiv;
> > + u32 kdiv;
> > +
> > + cnl_wrpll_decode_divs(&p->wrpll, &pdiv, &qdiv, &kdiv);
> > +
> > + pll_freq = skl_wrpll_calc_freq(ref_clock,
> > + p->wrpll.dco_integer, p->wrpll.dco_fraction,
> > + pdiv, qdiv, kdiv);
> > + drm_WARN_ON(&i915->drm, pll_freq != p->clock);
> > +
> > + if (clock == pll_freq)
> > + return true;
> > +
> > + return false;
> > +}
> > +
> > static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
> > struct skl_wrpll_params *pll_params)
> > {
> > @@ -3014,7 +3038,7 @@ static bool icl_calc_dp_combo_pll(struct intel_crtc_state *crtc_state,
> > int i;
> >
> > for (i = 0; i < ARRAY_SIZE(icl_dp_combo_pll_24MHz_values); i++) {
> > - if (clock == params[i].clock) {
> > + if (icl_dp_combo_pll_clock_match(dev_priv, clock, &params[i])) {
> > *pll_params = params[i].wrpll;
> > return true;
> > }
> > --
> > 2.25.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Ville Syrjälä
> Intel

--
Ville Syrjälä
Intel